[freeperfromnj]

I'm more interested in knowing why the flights were cancelled, where the intelligence came from

This BBC article seems to indicate that it's related to security concerns at LAX.

France-US flights halted in alert

The French Government has ordered the cancellation of several Air France flights to Los Angeles following a security alert.

The cancellations were requested by the US embassy in Paris - which mentioned fears of a terror attack, French officials said.

The services were scheduled to fly from Paris to Los Angeles on Wednesday.

The cancellations come amid a huge security operation at Los Angeles International Airport (LAX).

Private vehicles have been banned from the terminals amid fears of a terror attack.

[Steve_Seattle]

This BBC article seems to indicate that it's related to security concerns at LAX.

If there's a security problem at LAX, it probably wouldn't be limited to just these three flights, would it? To me, it sounds more like a problem with these specific flights, something on-board.